Ink jet printer with high capacity tank and associated ink refilling system

ABSTRACT

The ink jet printer comprises a printhead ( 22 ) movable in front of a printing medium ( 30 ) and provided with an ink cartridge ( 25 ) integral with it; the cartridge is filled with ink from a main, high capacity tank ( 35 ), which is connected at intervals to the cartridge ( 25 ) by means of a capillary element. During each connection, the capillary element ( 101 ) is brought into contact with the sponge ( 41 ) inside the cartridge, while a peristaltic pump ( 134 ) mounted integral upon the main tank provides a pressure suitable for generating a sufficient flow of ink to refill the cartridge ( 25 ) in a short time frame. To perform the refilling, the cartridge is brought at the end of its stroke into a service station ( 5 ) mounted on the body of the main tank ( 35 ), which is moved against the cartridge by means of a motor-driven linkage, controlled by a refilling management programme, in response to the signals of a cartridge ink level sensor.

This is a U.S. National Phase Application Under 35 USC 371 and applicantherewith claims the benefit of priority of PCT/IT03/00297 filed on May19, 2003, which was published Under PCT Article 21(2) in English, and ofApplication No. TO2002A000428 filed in Italy on May 20, 2002. Thecontents of the applications are incorporated by reference herein.

TECHNICAL FIELD

This invention relates to an ink jet printer provided with a main inktank and to a system for refilling the printer with ink.

The printer, according to the invention, is preferably applied in theretail sales sector, where a large number of transactions are performedevery day, such as points of sale (POS) at supermarkets, hypermarkets,and also in banks and post offices, where receipts have to be handedover and/or commercial documents printed with monochromatic ink, or inthree colours.

The colour version is more suitable for those commercial outlets thatgive great importance to their image, such as jewellers' shops,boutiques, quality clothes stores, which generally give out small sizesales slips and/or receipts, showing off their logo.

The printer according to the invention is intended mainly, though notexclusively, for the barrier applications where the operations takeplace in contact with the public and therefore require a high degree ofreliability and high speed operation in order not to add on uselessdelays due to printing; in addition, the printer according to theinvention offers low cost operation, a decidedly higher printing qualitythan that which may be obtained with thermal printers, and makethree-colour printing possible.

These requirements are obtained easily with an ink jet printer accordingto the invention, with which printing may take place not only on commonpaper, but also on different media and in different formats, such ascheques, sale slips, customer invoices, paper ribbons, etc., resultsthat cannot be obtained from thermal printers.

The better printing quality typical of an ink jet printer is necessarynot only for better readability, but also for printing of the commercialoutlet's logo, whether monochromatic or colour, and for printing of thebar code, which provides unique identification of each receipt, and forwhich perfect printing definition is essential for it to be detectedcorrectly, for example in the case of goods exchanges, where theinformation contained in the company database needs to be traced simplyby scanning the receipt.

BRIEF DESCRIPTION OF THE STATE OF THE ART

Equipment of various types is known in the art arranged for the realtime printing of receipts for payments, or sales slips; this equipmentis provided with ink jet printers, generally provided with alow-capacity ink cartridge, especially on account of dimensions; theseprinters do not however seem suitable for points of sale due to theircosts of management and due to the limited life of their ink cartridges,which must be replaced frequently, causing annoying delays for thecustomer, who has to wait to pick up the receipt, with resultantdiscomfort and wasting of time.

European patent application N^(o) 1.142.713 proposes an ink jet printerfor points of sale, which attempts to overcome the above-mentioneddrawback; this European application describes a printer in which asecondary tank integral with the mobile printhead is connected to amain, fixed ink tank, by means of external tubes for refilling theprinthead with the aid of a pump and cut-off valves.

The pump and valves are regulated by a control circuit, which processesthe signals generated by an ink level measuring device, consisting of amobile float, contained in the secondary tank. The float bears apermanent magnet, which in the vertical movement of the floatsuccessively faces on to one or the other of two fixed magnetic fielddetectors, arranged on a wall of the secondary tank; accordingly theresponse of the level measuring device is not continuous, passing fromthe full condition to the empty condition, but presents a maximum whenthe magnet is perfectly facing one or the other magnetic detector, butin the intermediate positions, the response of the measuring devicereaches a minimum before rising to one or the other of the maximumvalues, according to the direction of movement of the float.

This printer is very complicated to build and is subject to faults dueto the presence of hydraulic connections between the main, fixed tankand the movable printhead, in which the connection tubes, having to movein order to follow the movement of the printhead, are subject tocontinuous bending, with a high risk of breaks and losses of ink.

In addition the system of detecting the level of ink in this printer,being made of moving parts, is subject to jamming easily and/orunexpected malfunctions. Besides, the indications of the level measuringdevice are not exact, as they are affected by errors produced bynon-linearity of the response of the magnetic sensors employed and byhysteresis phenomena of different signs, depending on the direction ofmovement of the float.

SUMMARY DESCRIPTION OF THE INVENTION

Therefore the object of this invention is that of producing an ink jetprinter provided with a high capacity ink tank and the associated inkrefilling system without the drawbacks found in similar devices in theknown art.

In particular one object of this invention is that of producing an inkjet printer employed at points of sale (POS), in which the ink cartridgeintegral with the printhead, movable with respect to a printing medium,is refilled from a separate ink tank, mounted on the structure of theprinter, to which the cartridge is connected at intervals, determined bythe measurement of the level of ink contained in it.

Another object of this invention is that of using, for measuring thelevel of ink contained in the cartridge, a static resistive detector,fixed inside the cartridge and suitable for detecting with continuityand linearity the level of ink in between the cartridge full situationand the cartridge substantially empty situation.

Still another object of this invention is that of making an ink jetprinter in which the service, or movable printhead parking, positioncoincides with the ink refilling position.

A further object of this invention is that of producing an ink jetprinter provided with an innovative head cleaning system in which thecleaning blade loaded with the ink just removed from the head isreplaced by another clean blade.

In accordance with the envisaged objects of this invention, an ink jetprinter is proposed, provided with a high capacity ink tankcharacterized in the way defined in the main claim.

The characteristics of the invention will be seen clearly from thefollowing description of a preferred embodiment, provided by way ofnon-restrictive example, with reference to the figures of the drawingsattached.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an external perspective view of an ink jet printeraccording to this invention employed at points of sale (POS);

FIG. 2 represents a perspective view of the inner structure of theprinter of FIG. 1;

FIGS. 3 a, 3 b represent respectively a perspective view of the inkcartridge integral with the printhead and a median section of the same;

FIG. 4 represents a partially sectioned perspective view of the maintank and of the head in the position of recovery and simultaneousrefilling;

FIG. 5 represents a perspective view of the recovery and refillingstations, mounted on the main tank;

FIG. 6 represents an exploded perspective view of the recovery andrefilling stations of FIG. 5;

FIG. 6 a represents a perspective view of the recovery and refillingstations, mounted on the main tank in the case of a colour printer;

FIG. 7 represents a median section of the main tank of FIG. 5;

FIG. 8 represents a perspective view of the flexible pouch for the ink,inserted in the main tank;

FIG. 9 represents an exploded perspective view of the printhead cleaninggroup;

FIGS. 9 a, 9 b represent an external perspective view of the group ofFIG. 9 and the system for retrieving the cleaning blade;

FIG. 10 represents in perspective a group of the equipment of FIG. 2,comprising the paper path;

FIG. 11 depicts in elevation a lateral view of the group of FIG. 10;

FIG. 12 depicts an internal view of the group of FIG. 10;

FIG. 13 depicts the group of FIG. 12 in overturned position to accessthe paper roll;

FIG. 14 represents in perspective an ink pumping device mounted on themain tank;

FIG. 15 depicts an exploded perspective view of FIG. 14;

FIG. 16 represents a perspective view of the main tank incorporating apumping device for three inks of different colours;

FIG. 17 represents a detail of FIG. 16.

FIG. 18 represents the ink level detecting circuit;

FIG. 19 indicates the flow of instructions for the preparation of a newhead mounted on the printer of FIG. 2;

FIG. 20 represents the flow of instructions that regulate the processfor refilling the cartridge;

FIG. 21 is an exploded perspective view of an alternative embodiment ofthe main tank of FIG. 5, for use on a monochromatic printer;

FIG. 22 represents a section view of a valve of the main tank of FIG.21; and

FIG. 23 represents a longitudinal section of a version of the main tankalternative embodiment of FIG. 21, for use on a colour printer.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, the printer that this invention relates to isincorporated in equipment, generically indicated with the numeral 1, forthe release of receipts for payment printed on pieces of a strip ofpaper, or sales slips, or on printing media supplied by the clients,this equipment 1 being intended preferably in combination with a cashregister at the so-called points of sale (POS), for instance in ahypermarket.

The equipment 1 is inserted in a casing 2 substantially consisting ofthree parts separated ideally by a separation line 3 between a baseportion 4 and the rear part 5 and by a line 6 corresponding to theinternal paper path 7 described later, which separates a front block 8from the base 4 and from the rear part 5; the base 4 prevalentlycomprises the section electronically controlling and managing the entireequipment item. The rear part 5 encloses a number of auxiliarymechanical groups mounted on an auxiliary frame, such as an automaticcutter, a seat for a roll of paper and a main, high capacity ink tank.

The front block 8 encloses a printing group, comprising a mobileprinthead with its own cartridge and mechanisms for driving theprinthead and for feeding the various printing media, not depicted inFIG. 1.

In the front part, the casing 2 presents a horizontal aperture 9 fromwhich a support plane 10 protrudes for inserting the documents on whichprinting is to take place.

In the top part, the casing 2 presents at the end of the paper path atransversal slot 11 from which are ejected both the printed documents,entered in the aperture 9, and the receipt slips, not shown, which arecut by the operator by means of a cutter 12 placed in the slot 11. Alsolocated on the top part of the casing is a small console 14 containing anumber of buttons for control of the whole item of equipment.

On the whole, the casing 2 stands out on account of its extremelycompact size, so as not to take up too much space on the cashier's workplane.

FIG. 2 shows in perspective the inner structure of the equipment 1, withthe relative mechanical components borne by a main frame 20; in greaterdetail, mounted on the frame 20 is a printing unit 21, comprising an inkjet printhead 22, joined integrally with its own ink feeder cartridge25, of the refillable type and containing a spongy body, not visible,which retains the ink in its capillary cavities; the head 22 andrelative cartridge 25 are mounted on a movable carriage 26, driventransversally by a motor 23, by means of a belt 27, along horizontal andfixed guides 28.

The printhead 22 is suitable for printing on print media of differenttypes and formats, among which a strip of paper 30, on which the logo,or trading name of the commercial outlet and a list of the transactions,with the total to be paid and any change are normally printed; the strip30 is cut into sales slips by the operator by means of the manual cutter12 and handed over to the customer, or at the operator's discretion by aknown type of automatic cutter 34, arranged on the top part 34 a of theequipment 1.

The strip 30 unwinds from a roll 32, disposed in an internal seat 33 andnot visible in FIG. 2, which can be reached by throwing back the toppart 34 a (FIGS. 12, 13).

The printhead 22 is also suitable for printing on paper media of largerdimensions than the ribbon 30, for instance customer invoices, cheques,etc. These documents are inserted on a front plane 10 and are started bymeans of feeding rollers 37, moved by a motor 38 (FIG. 10) towards theprinting area, along a paper path 36 (FIG. 2), that starts on thesupport plane 10 and finishes in correspondence with one of the cutters12, or 34.

Arranged along the paper path, as is known in the sector art, aresensors which, in association with an electronic control unit, not shownin the drawings, control the motor 38 for feeding the documents firstwith a continuous motion towards the printhead 22, and then with adiscrete pitch motion (line feed), during printing.

On the right hand side of the equipment 1 is a large capacity tank forthe ink 35, for instance of 200 ml, designated main, in that, as will bedescribed later in detail, it is intended to refill the cartridge 25;the tank 35 is positioned in correspondence with an end-of-stroke E ofthe printhead 22 (on the right in FIG. 2), where the so-called servicestation S (FIG. 5), in which the head 22 parks each time that itcompletes a print operation, is also positioned.

Therefore in the printer according to this invention, the printheadstops in a sole position E of its stroke, whether for its parking andcleaning operations, or for refilling with ink, whenever necessary.

Printing Unit

The known type printing unit 21 is depicted in FIGS. 3 a and 3 b, towhich reference is made, respectively with a perspective view and alongitudinal section view; the unit 21 comprises the cartridge 25 forthe ink and the known type of ink jet printhead 22; the cartridge 25 ismade of a substantially parallelepiped container 40, containing a spongybody 41 with communicating cells, capable of storing by capillarity agiven quantity of ink. The known type of ink jet printhead 22 is mountedintegrally on a back wall 42 of the cartridge 25, supported by aprotruding portion 42 a of the wall 42, and is made up of a plate ofsilicon 44 bearing a plurality of layers in which are built the ejectionchambers, the heating elements (resistors) and a corresponding pluralityof ink droplet ejection nozzles 45, fed by the spongy body 41 through aninternal duct 46.

The cartridge 25 is closed by a lid 47, opposite the wall 42, mounted onwhich are two electrodes 48, extending into the inside of the spongybody 41, and having the function of sensor Rs (FIG. 19) of the level ofink inside the cartridge 25; the sensor Rs detects the electricalresistance of the ink contained inside the sponge 41, in the spacebetween the electrodes 48, encountered by a current pulse applied to theelectrodes; the two electrodes 48 protrude externally from the lid 47with corresponding metallic buttons 49, in order to be connected to acircuit CR (FIG. 18) for detecting the level of ink contained in thecartridge 25; the circuit CR is not described in detail herein as it hasalready been published in the Italian Patent N^(o) 1.245.065.

The printing unit 21 is blocked on the carriage 26 (FIGS. 3 b, 4) bymeans of a lever 51, hinge-mounted on the carriage 26 and rotatedanti-clockwise into a closed position, against the lid 47 of thecartridge 25, wherein the lever 51 is blocked by a catch 52, visible inFIG. 4. The lever 51 bears two contact probes 53, arranged so as to makean electrical contact with the two corresponding buttons 49; the twocontact probes 53 are electrically connected to a flat cable 55, throughwhich the signals necessary for determining the level of ink inside thecartridge 25 are transmitted to the detecting circuit CR; the flat cable55 is electrically connected to another flat cable 55 a (FIGS. 2, 4)bearing the printing and head 22 displacement signals.

To increase the autonomy of the printer 22, the cartridge 25, accordingto the invention, may be refilled with ink at regular intervals, definedby the detecting circuit CR, without being bound to substitute the emptycartridge, or extract it for refilling, thereby interrupting a printingoperation in progress.

Refilling of the cartridge 25, according to this invention, occurs bytransferring the ink from the main tank 35, of high capacity withrespect to the capacity of the cartridge 25, disposed in an appropriateseat 57 (FIG. 2), supported by the frame 20.

Therefore as the refilling with ink from the main tank 35 to thecartridge 25 can occur very frequently, even during each stoppage of thehead 22 in the service station S (FIG. 5), the dimensions and capacityof the cartridge 25 may be highly reduced in comparison with thecartridge of a non-refillable head, i.e. a “throwaway” type head.

By way of non-restrictive example, it is assumed that the cartridge 25may contain a minimum of 3 cc. and normally 5 cc. of ink, whereas themain tank 35 may contain up to 200 cc. of ink; therefore before the maintank 35 runs out of ink, about 40 refills may be made.

The main tank 35 is made of a plastic, parallelepiped container 58(FIGS. 4, 7), having an upper wall 59 that is removable so that acollapsible pouch 60 of highly flexible impermeable material, forexample polyethylene aluminate (FIG. 8), may be inserted from above intothe container 58. The pouch 60 is welded at the bottom to arhomboid-shape cap 62, provided with a lateral refilling hole 64, closedin use by a plug 65 (FIG. 5), for refilling with ink and a stretch ofoutlet tube 66, used for feeding the refilling means of the cartridge25, in the way that will be described below.

To avoid sudden interruptions of the printing activity of the head 22,refilling of the cartridge 25 with the ink drawn from the main tank 35,is performed when the printhead 22 is in the end-of-stroke position E(FIG. 2), beyond the end of a line of print, in correspondence with theservice station S (FIG. 4), where the head 22 is cleaned and where it isparked in idle periods in a closed, humid environment, to avoid the inkin the nozzles from drying.

The service station S is mounted on a self-standing, plastic structure68 (FIGS. 5, 6), suitable for being removably connected by means ofcatches 69 to the container 58 of the main tank 35 and in particular,according to one aspect of this invention, the structure 68 is mountedon a front wall 70 of the container 58 and can make small verticalmovements in contact with the wall 70, thanks to the sliding engagementof the catches 69 between the corresponding slots 69 a, as may be seenlater.

The service station S comprises a soft rubber cap 72, rectangular shapedin plan view, provided with a continuous embossed edge 73, which is keptin contact with a front face 43 (FIG. 3 a) of the head 22, so that allthe nozzles 45 are enclosed inside.

The cap 72 is mounted on a plastic support 74 (FIGS. 5, 7) elasticallyresilient in the support direction of the cap 72, in that the support 74can travel for a brief stroke in a protruding seat 75, that is part ofthe structure 68, against the action of a spring 76.

Head Cleaning System

During printing it is known that a certain amount of ink remainsdeposited on the outer surface around the nozzles; it is necessarytherefore to clean the head after a certain time interval, to avoiddirtying the medium that is being printed on.

For this purpose, on the ink jet printer, according to the invention, acleaning system has been arranged that comes into action each time thehead stops in correspondence with the service station S.

The system for cleaning the nozzles 45 of the printhead 22 (FIG. 3 a)comprises a cleaning group P (FIGS. 5, 9), mounted on the structure 68,beside the cap 72, in a position preceding the cap in the directionalong which the head 22 approaches the service station S. The cleaninggroup P is enclosed in a support case 78, provided with guides 79coupled with corresponding counterguides 80 integral with the structure68 (FIG. 6), so as to allow the cleaning group S to perform limitedmovements towards and away from the head 22. In fact, the cleaning groupP must be removed from the trajectory of the head when the latterapproaches the end-of-stroke position E, and must subsequently bebrought closer to the head in order to perform cleaning of the nozzleswhile the head is in the service station S. In particular, the cleaninggroup P is kept removed from the structure 68 by an elastic member 81,(FIG. 9 b), placed between the case 78 and the structure itself.

The cleaning group P comprises a rotating disc 82, made of soft, elasticrubber, built with a plurality of radial expansions, or cleaning blades83 (FIG. 9), for instance four cleaning blades 83 arranged at 90° onefrom the other; each blade 83 has a rectilinear edge 84, which, inoperation, is arranged parallel to the front face 43 (FIG. 9 a) of thehead 22 so as to slide over it in order to remove the ink depositedaround the nozzles during printing, which by drying could adverselyaffect efficiency of the nozzles.

The disc 82 is mounted on a bushing 85 by means of a cross-shapecoupling element 86; the bushing 85 is in turn mounted on a pin 87integral with a toothed wheel 88, by means of a known type ofunidirectional clutch, consisting of a helical spring 89, inserted withplay between the bushing 85 and the pin 87, pivotingly mounted on thesupport case 78. When the wheel 88 is rotated in a direction such as tocause an increase in the diameter of the spring 89, the bushing 85 andtherefore the disc 82 are driven in rotation. Vice versa, the bushing 85remains motionless when the toothed wheel 88 is rotated in the oppositedirection, when the diameter of the spring decreases.

Also mounted on the case 78 is an ink collecting element 90 shaped as anopen ring, arranged concentrically facing the disc 82, and provided witha knurled surface 92, placed in contact with one face of the disc 82 andsuitable for removing from the disc 82 the ink accumulating during eachhead cleaning operation.

To prevent an excessive amount of ink accumulating on each of the blades83, the disc 82 is rotated by 90° anti-clockwise (in FIG. 9 b) aftereach scraping operation, by means of a feeding device 94 (FIG. 9 b),consisting of a toothed rack 95 sliding on one of the guides 79 of thecase 78 and meshing with the toothed wheel 88. Between the toothed wheel88 and the disc 82 is a known type of uni-directional clutch 89; therack 95 is stably connected with the structure 68, i.e. to the tank 35,through a stiff arm 96.

The feeding device 94 is actuated by means of the same alternatingapproach/retract movement of the tank 35 in the direction of theprinthead 22, used also in the refilling phase, which will be describedbelow.

Each time the head 22 reaches the service station S, the cleaning groupP finds itself in a retracted position, and therefore the head 22 goespast it without any interference and stops in the service station S, asis shown in FIG. 4.

At this point, the tank 35 is made advance until an arm 97 (FIGS. 5, 9)protruding from the case 78, engages with the front wall 42 of the head22, causing the cleaning group P to stop. Further feeding movement ofthe tank 35 results in the structure 68 drawing relatively closer to thecleaning group P, overcoming the action of the elastic member 81, whichcompresses. During this approach phase, the toothed wheel 88 is rotatedby the rack 95, firmly connected to the tank 35; the toothed wheel 88 inturn connects with the bushing 86, thanks to the uni-directional clutch89, and produces the anti-clockwise rotation (FIG. 9 b) of the disc 82through an angle of 90°, bringing the blade 83 dirty with ink to slideagainst the collecting element 90, and positioning the next clean bladein front of the head 22.

Subsequently the head 22 is moved a number of times back and forward infront of the cleaning group P so as to slide the cleaning blade 83against the nozzles, to remove the ink deposited there. During thismovement of the head 22, the arm 97 comes into contact with a frontsurface of the carriage 26 in order to keep the disc 82 at the rightdistance from the head 22, so that the edge 84 slides over the frontsurface 43 of the head 22 with the right amount of interference.

Subsequently the tank 35 is retracted; the elastic member 81 isreleased, thus re-establishing the original distance between thecleaning group P and the structure 68. During this relative motionbetween the group P and the structure 68, the rack 95 causes the toothedwheel 88 to turn idly, i.e. without transmitting motion to the cleaningdisc 82, since the unidirectional clutch 89 is not active.

The blades 83 may also be of a number other than four, and it will beobvious generally that if the number of blades such as those designatedwith the numeral 83 is increased, functionality of the disc 82 willimprove; however, it is considered that four expansions represents agood compromise between optimization of the disc 82 and overalldimensions of the cleaning group P.

Ink Refilling System

As anticipated earlier, to increase efficiency and autonomy of theprinter, and to prevent sudden interruptions of printing, or moregenerally to lower the management costs, the cartridge 25 of the head 22may be repeatedly refilled with ink from the main tank 35 each time itis motionless in the service station S and the detecting circuit CRdetects a shortage of ink in the cartridge 25.

To satisfy these requirements, according to one aspect of thisinvention, refilling means 100 (FIGS. 5, 7) are provided, which takeadvantage of the characteristic of a capillary element 101, to effectthe transfer of ink from the main tank 35 to the cartridge 25, byputting said capillary element 101 in hydraulic contact with the spongybody 41 contained in the cartridge 25 for short periods. Precisely forthis purpose, a hole 50 is made in the wall 42 of the cartridge 25 (FIG.3), which leaves a part of the spongy body 41 in view.

The refilling means 100 are mounted on the same autonomous structure 68that bears the service station S, in a higher position than the latter.Said refilling means 100 consist of the capillary element 101 with highcapillarity, protruding frontally from a protective cover 102, set inalignment with the hole 50 in the cartridge 25 (FIG. 3 a) whenever thelatter, mounted on its carriage 26, is motionless in the service stationS.

The capillary element 101 comprises a cylinder made of a highcapillarity, spongy material, housed in an appropriate seat 104 (FIG. 7)produced in a support 105, on the inside of the support structure 68.

Alternatively the capillary element 101 may be replaced by a fibrouselement, consisting of a bunch of parallel fibres packed inside the seat104 during the assembly stage.

The seat 104 communicates with one end of a feeding duct 106, preferablymade from a flexible, silicon tube 107, which is connected at the otherend with the main tank 35 and more precisely with the outlet tube 66(FIG. 8) of the pouch 60.

As already anticipated above, the cartridge 25 is refilled with ink,when required by the detecting circuit CR, by placing the capillaryelement 101 in hydraulic contact with the spongy body 41.

For this purpose, according to another aspect of the invention,advancing means 112 (FIGS. 10, 11) are included, which move the tank 35in a direction perpendicular to the stroke of the head 22, to bring therefilling means 100 against the cartridge 25 and in particular to placethe fibrous element 101 in hydraulic contact with the spongy body 41 ofthe cartridge 25.

The container 58 of the main tank 35 is in turn arranged in a rigidhousing 57 (FIGS. 2, 4) open at the top, and is kept blocked therein bymeans of a lever 110.

The housing 57 is mounted slidingly on two pins 113 (FIGS. 2, 10)integral with the frame 20 of the equipment 1, which engage with twopairs of slots 114, made in opposite sides of the housing 57 (FIG. 4).

The advancing means 112 (FIGS. 10, 11), which provide the housing 57, orrather the main tank 35 contained therein, with movement, comprise amotor 116, which through a gear train 117 moves a rack 118, connected toa slide 119. The rack 118 and the slide 119 are mounted slidingly onfixed pins 120, which engage with corresponding rectilinear slots 121.

The slide 119 is provided with a laterally protruding thrust tab 122,which engages with a projection 124 protruding laterally from thehousing 57 (FIG. 4).

Accordingly the main tank 35 can move by the amount necessary to bringthe refilling means 100 alongside the cartridge 25, stopped in theservice station S, and insert the capillary element 101 through the hole50 in the cartridge 25 until hydraulic contact is made with the sponge41, in such a way as to set up a flow of ink from the tank 35 to thecartridge 25 through the capillary element 101.

At the end of each refilling operation, the motor is activated to movethe slide 119 in the opposite direction, while the housing 57 isretracted due to the action of a recall spring not depicted in any ofthe drawings.

In order to greatly reduce the refilling time, the refilling means 100comprise, according to the invention, an auxiliary ink feeding device126, associated with the capillary element 101, for increasing thestream of ink transferred from the tank 35 to the cartridge 25.

The auxiliary feeding device 126 is arranged along the course of thefeeding duct 106, downstream of the pouch 60, and is mounted on anauxiliary frame 128 of its own, suitable for being removably fixed bymeans of elastic catches 130 to the lower part 132 of the container 58,thus making a rear wall of the same container (FIGS. 7, 14).

The auxiliary feeding device 126 consists of at least one peristaltictype pump 134 (FIG. 14), known to those acquainted with the sector art,comprising at least three rollers 135 (FIG. 15) mounted on the peripheryof a rotating pulley 136; the rollers 135, by the fact of rolling,compress a section 138 of the tube 107, wound in an open ring around thepulley 136, inside a ring-shaped housing 139. The auxiliary frame 128also has another two housings 139 a, 139 b, identical to the housing139, pre-arranged, as will be described in the following, for the use ofthree different colour inks, for instance red, cyan and blue.

Operation of the peristaltic pump 134 is obvious: each roller 135compresses the tube 107 and in its rolling movement gradually compressessuccessive zones of the section 138 of the tube 107, pushing the inkforward towards the capillary element 101; downstream of the roller 135,through the effect of its elasticity, the tube 107 regains its originalshape, creating inside a depression which calls up more ink from thepouch 60.

The pulley 136 is provided with front toothing 140, protruding from theside opposite the rollers 135, and suitable for meshing frontally with adrive pulley set in motion by a motor, located in the bottom part of theframe 20.

Each time the detecting circuit CR detects a level of ink in thecartridge 25 less than a predefined value, the motor 116 is started formoving the slide 119 (FIG. 11) towards the front part of the equipment 1(on the left in FIG. 11). The tab 122, in mesh with the protrusion 124of the housing 57, moves the tank 35 forward to set the capillaryelement 101 in contact with the sponge 41 inside the cartridge 25. Atthe same time, the pump 134 is actuated in response to a refillingmanagement programme, based on the level of ink detected in thecartridge 25, providing the capillary element 101 with a suitable streamof ink, in order to lower the time for refilling of the cartridge 25.

During the phase in which the tank 35 is brought alongside the cartridge25, to ensure perfect alignment between the capillary element 101 andthe hole 50 in the cartridge 25, the support structure 68 (FIG. 6) ismoved with respect to the container 58, on which it is mounted, throughthe action of an inclining profile 142 of a pair of protruding arms 143,attached to the structure 68 and set in engagement with the carriage 26.A peg 145, also protruding from the structure 68, actuates a microswitchin order to stop the advance of the tank 35 when the capillary element101 has reached the correct position of hydraulic contact with thesponge 41 of the cartridge 25.

FIG. 12 illustrates the path of the strip of paper 30 in the situationof normal operation, wherein the support frame 35 of the cutter 34 is inthe closed position. The strip 30 unwinds from the roll 32, passesaround the driving rollers 37, and exits by the top in front of thecutter 34.

FIG. 13 shows the support frame 35 in the thrown-back positionpermitting access to the housing 33 of the paper roll 32, for replacingit.

In the description above, reference was made to a preferred embodimentof the printer according to the invention, equipped for printing with asingle ink, for instance black. Naturally the prefixed objects of theinvention are not changed in the slightest in the case of a colourprinter using the three basic colours, red, cyan and yellow.

In this case, the container 58 houses three pouches 60, each filled withan ink of one of the basic colours. The refilling means 100 use threecapillary elements 101 a, 101 b, 101 c, one for each colour, (FIG. 5 a).Similarly the cartridge 25 contains three compartments filled with inksof the basic colours, and has three holes 50 to permit hydraulic contactbetween the three capillary elements 101 and the three sponges of thecartridge 25. The auxiliary feeding device 126 consists of threeperistaltic pumps 147, 148, 149 (FIGS. 16, 17), each working on acorresponding section of the three ducts 106, which connect each pouch60 with the corresponding capillary element 101.

The three pumps 147, 148, 149 are mounted on the same auxiliary frame128 shown in FIG. 15 used for the single-colour printer; in fact, thisframe is provided with three identical housings 139, 139 a, 139 b.

According to an alternative embodiment of the main tank 35, asrepresented in FIG. 21, the collapsible pouch 60 (FIG. 8) is substitutedby a rigid compartment, made in the main tank 35 (FIGS. 3, 4); moreparticularly, in the case of a black and white printer, the main tank 35comprises a container 258 (FIG. 21), made of lateral walls 259, a rearwall 260 and an upper closing wall 262, all of rigid plastic andreciprocally welded in such a way as to make the container 258 closedwith perfect hydraulic sealing.

The container 258, built according to this alternative embodiment,comprises a single compartment 263 suitable for being filled with blackink, during construction.

The rear wall 260 is provided with an outlet pipe 66, not shown andsimilar to that previously described in relation to FIGS. 7 and 8,suitable for being connected with the silicon tube 107 so as to refillthe auxiliary feeding device 126 (FIG. 21) with ink.

On account of the stiffness of the walls 259, 260, 262 of the container258, the pressure inside the container 258 would tend to dropsignificantly as the ink is withdrawn from the auxiliary feeding device126, until feeding of the ink is interrupted.

To avoid this happening, according to this alternative embodiment, adevice 265 (FIG. 21) compensating the pressure inside the container 258,with respect to the outside pressure, is provided for use.

The compensating device 265 comprises a small one-way valve 266 (FIG.22), fitted on the top wall 262 and which has the function ofintroducing air from the outside into the container 258, as the inkcontained therein is consumed, for compensating the pressure inside thecontainer, with respect to the ambient pressure.

The valve 266 is preferably made of a round, concave disc shaped elasticelement 267 (FIG. 22), mounted on a support 268, in turn inserted in ahole 269 in the wall 262; a rod 270 bearing the valve 266 is inserted ina central hole of the support 268, by such an amount that the edge 271of the disc 267 rests gently on the surface of the support 268, with itsown convexity facing the inside of the container 258.

The support 268 is also traversed by a number of communication holes 272arranged on the inside of the edge 271 of the disk 267 and hence of theumbrella surface defined by the same disk 267.

Therefore, when the pressure inside the container 258 drops with respectto the external pressure, the outside air pressing against the convexsurface of the disc 267, lifts the edges 271 and flows into thecontainer itself, bring the pressure inside to a level close to that ofthe external pressure.

Similarly, in the case of a colour printer as well, the container 258comprises three compartments 275, 276, 277 separated by rigid walls 278,280 (FIG. 23), soldered to the walls 259, 260 and 262 of the container258; the three compartments 275, 276 and 277 therefore act as threesealed tanks for the three colour inks, replacing the collapsiblepouches, similar to the pouch 60 (FIG. 8).

On the top wall 262 of the container 258 (FIG. 23) three devices 282,283 and 284 are provided compensating the internal pressure of eachcompartment 275, 276 and 277, fully similar to the valve device 266(FIG. 22), and which are therefore not described in detail, forbrevity's sake.

The three compensating devices 282, 283, 284 operate fully independentlyeach from the other, depending on the pressure variation inside eachcompartment 275, 276, 277, generated by the different quantity of colourink withdrawn by the auxiliary feeding device 126, for feeding therefilling device 100.

Management and Control of Refilling with Ink

Management and control of the phases of refilling the cartridge 25 withink from the main tank 35 is handled by a known type of electronic unit,which also manage all the other functions of the printer according tothis invention.

In particular the control unit receives the signals regarding the levelof ink conditions inside the cartridge 25, from the detecting circuit CR(FIG. 18).

Each time a new, original head is fitted in the printer, it undergoes aninitialization procedure (FIG. 19), for loading in a memory M (FIGS. 3a, 3 b) incorporated in the cartridge 25, a number of reference dataitems used by the printer in later use of the head, such as:

the FULL value, of cartridge full of ink;

the REF value, for normal reference for commencing refilling;

the LOW1 value, upper limit of the intervention window;

the LOW2 value, lower limit of the intervention window, corresponding toa cartridge empty situation.

The initialization procedure is conducted in the following steps (FIG.19):

step 150: a current pulse is applied to the sensor Rs;

step 151: the CR circuit detects a resistance value corresponding to thecartridge full condition (FULL);

step 152: the ambient temperature in a zone adjacent to the cartridge 25is measured in one of the ways known in the sector art;

step 153: the temperature measured is compared with a reference value of25° C.;

step 154: if the temperature measured is 25° C., the FULL value detectedin step 151 is stored in the memory M;

step 155: if the temperature measured is other than 25° C., the FULLvalue detected in step 151 is calculated again on the basis of thecurrent value of the temperature by means of a conversion algorithmstored in the memory M, and then stored;

step 156: calculation and storage of the REF value, between 40% and 60%of FULL;

step 157: calculation and storage of the LOW1 value, between 35% and 45%of REF;

step 158: calculation and storage of the LOW2 value, generally lowerthan REF;

step 159: storage of the values of other parameters used in managementof refilling and also in operation of the head, such as: conductivity ofthe ink; manufacturing tolerances on position of the electrodes 48;tolerances of the components of the CR circuit; number of dropletspossibly already ejected, for taking stock of non-new heads; etc.

After performing initialization of the head, the electronic managementunit is capable of following the trend in consumption of ink by the headduring printing. Management of ink refilling therefore takes placeaccording to the following steps (FIG. 21):

step 160: the management unit checks if a head is present in thecarriage 26;

step 161: reading from the memory M on board the cartridge 25 of theFULL, REF, LOW1 and LOW2 values;

step 162: reading from the memory M of the number of droplets alreadyejected;

step 163: comparison of the number of droplets ejected with thatrelative to the head's life span;

step 164: if the head has completed its life, a head substitutionmessage is output;

step 165: if the head can go on printing, the value of the ambienttemperature in the vicinity of the head is read;

step 166: comparison of the temperature measured with the value of 25°C.;

step 167: if the temperature measured is other than 25° C., the valuesfor FULL, REF, LOW1 and LOW2 are re-calculated;

step 168: if the temperature measured is 25° C., the sensor Sr isactivated for obtaining the current value of the level of ink in thecartridge 25;

step 169: the current level value is compared with the calculated valuesLOW1 and LOW2;

step 170: if the level is lower than LOW1, the control unit actuates themotor 116 (FIG. 10) to bring the tank 35 alongside the cartridge 25 andmake hydraulic contact between the capillary element 101 and the sponge41; the pump 134 (FIG. 14) is activated for refilling the cartridge, fora predetermined time;

step 171: activation of the sensor Sr for detecting the new ink level;

step 172: comparison between the level detected and the value REF;

step 173: if the level detected is greater than REF, this means that thecartridge 25 has been filled for more than 50% of the FULL value, andtherefore the control unit stops the pump 134 and commands retraction ofthe tank 35 and printing can continue;

step 174: if the level detected is lower than REF, a check is made tosee if the current level is greater than the level previously detectedat step 168;

step 175: if the comparison is passed, the procedure returns to step 170for activation of a new refilling cycle; if subsequently the level islower than REF, and no increase in the level was detected in step 174,then the main tank is empty, and so printing is resumed from step 173 inorder to use up the ink remaining in the cartridge 25;

step 176: if X dots have been printed with X a value in the order ofmillions of dots, the number of droplets ejected is updated in step 177,and the process is repeated from step 163 to step 169, in which a levellower than LOW2 will surely be detected, so that in step 178 a messageto substitute the main tank 35 is displayed.

It will therefore be clear that, according to the invention, with asingle sensor Sr, placed on board of the cartridge 25 of the printhead22, it is possible to detect both the filling condition of the cartridge25, and that of the main tank 35.

1. An ink jet printer comprising: a printhead movable in front of aprinting medium; an auxiliary tank for ink integral with said printheadand containing a spongy body; a detecting circuit of a level of the inkin said auxiliary tank; a main tank for the ink, arranged on a frame ofsaid printer; and refilling means selectively activable for transferringa predetermined quantity of ink from said main tank to said auxiliarytank, at predefined time intervals; wherein said refilling meanscomprise at least one capillary element of high capillarity and anauxiliary ink feeding device associated with said capillary element,mounted on said main tank, said capillary element being suitable forestablishing hydraulic contact with said spongy body, for transferringthrough capillarity the ink from said main tank to said auxiliary tank,and said auxiliary ink feeding device being suitable for cooperatingwith said capillary element so as to increase the stream of inktransferred from said main tank to said auxiliary tank, when saidprinthead is parked in a service station, each time said detectingcircuit detects a level of ink in said auxiliary tank lower than aprefixed value.
 2. The printer according to claim 1, wherein said maintank supports said refilling means, said service station, and saidauxiliary ink feeding device.
 3. The printer according to claim 2,wherein said at least one capillary element and said service station aremounted on a support structure and said auxiliary ink feeding device ismounted on an autonomous frame, said support structure and saidautonomous frame being removably connected, by means of elastic catches,on a front wall and on a rear wall respectively of said main tank. 4.The printer according to claim 1, wherein said refilling means aredirectly connected to said main tank by means of a feeding duct ofelastic and flexible material, said duct cooperating with said auxiliaryink feeding device, for transferring ink from said main tank to saidcapillary body.
 5. The printer according to claim 1, wherein saidcapillary element is made of a cylinder of spongy material with highcapillarity, accommodated in a suitable seat made in said supportstructure.
 6. The printer according to claim 1, wherein said capillaryelement consists of a fibrous element, made from a bunch of parallelfibres, packed inside said seat in the assembly step of said refillingmeans.
 7. The printer according to claim 1, wherein said main tank isinserted in a housing mounted on pins, fixed to said frame, in slidingengagement with two pairs of slots of said housing, said housing beingmoved from a rest position, distant from said printhead to a refillingposition, in which said main tank is positioned in front of saidprinthead motionless in said service station, to allow said capillaryelement to refill said auxiliary tank with ink.
 8. The printer accordingto claim 7, wherein advancing means are provided for moving saidhousing, said advancing means comprising a motor cinematically connectedto a moving slide through a gear train, said slide being provided with athrust tab in driving engagement with a projection fixed on saidhousing.